Init payload iwth both username and query

`query` is a different parameter from `username` so it shouldn't replace
it actually. Tested with v3 API and it's working.

Author: eljulians

jira/client.py

@@ -2841,13 +2841,11 @@ def search_users(
 
         params = {
             "username": user,
+            "query": query,
             "includeActive": includeActive,
             "includeInactive": includeInactive,
         }
 
-        if query:
-            params["query"] = query
-
         return self._fetch_pages(User, None, "user/search", startAt, maxResults, params)
 
     def search_allowed_users_for_issue(